This proposal describes a 5-year training program for the development of an academic career in Transfusion Medicine. The PI has completed his Clinical Pathology residency and Transfusion Medicine Fellowship at the University of Pennsylvania (UPenn), and is developing both his clinical skills and his research career by studying erythropoietic differentiation using a novel short hairpin-loop RNA (shRNA) library. UPenn provides an ideal training environment by providing both intellectual and physical resources of the highest caliber, backed by a strong track record of winning career development awards. The PI will conduct his research under the mentorships of Dr. Robert B. Wilson, an internationally renowned geneticist, and Dr. Mitchell Weiss, an international authority on erythropoiesis. The PI will be advised by a committee of highly regarded scientists, including Drs. Donald Baldwin (Director of the UPenn Microarray Core), Zissimos Mourelatos (an expert on RNA interference), Mariusz Wasik (Director of Hematopathology), and Isidore Rigoutsos (Manager of IBM Bioinformatics). In addition, Dr. Donald Siegel, Vice-chair of Transfusion Medicine, will mentor the PI's clinical development. The proposed research exploits the recent discovery of RNA interference (RNAi), an important mechanism of genetic regulation. Unlike existing RNAi libraries, which have significant sequence bias and are expensive to make, the novel shRNA library constructed by the PI is unbiased and can be made at a fraction of the cost. The PI has identified shRNAs from the random library that confer protection from IL3-withdrawal-induced apoptosis, improved one of the hits through random mutagenesis, and shown that different hit shRNAs differentially alter gene expression patterns by microarray analysis. The PI will apply similar methodologies to further improve his hits and discover the specific gene sets altered by these shRNAs. He will also study the pathways modulated by his shRNAs during erythropoietic differentiation, either alone or in cooperation with erythropoietin signaling. Finally, he will use his library to discover novel shRNAs that can induce erythropoiesis themselves, and elucidate their mechanisms of action. The strength of this proposal is the use of a unique, random shRNA library to influence erythropoiesis in an agnostic approach, with obvious translational and therapeutic implications. Anemia is a major complication in chronic renal disease, and is the most common indication for transfusion. Therefore, the understanding and potential influence of erythropoiesis is particularly relevant to public health and the PI's said clinical interest. In the near term, the PI will focus on acquiring knowledge and developing his research skills in erythropoiesis, RNAi and bioinformatics. In the long run, the PI's career objective is to become an independent physician-scientist with roughly one quarter of his effort devoted to transfusion medicine and other three quarters to research on erythropoiesis.